Datasheet

FS98O22

Rev. 1.6 60/146

z Pulse Width Measurement mode:

Programmable Counter could be used to measure the time when a signal holds its voltage level in high or

low.

Operation:

1. Clear FQTMB and clear MUXSEL[2] register flags to make the Programmable Counter work as Pulse

Width Measurement.

2. Setup MUXSEL[1:0] to decide the input clock signal.

3. PFI is the signal which is ready to measure the pulse width. Users could set TE to invert the PFI voltage

level.

4. Clear OVAB register flag to set the CTA as the working counter. When CTA counter overflows, the

interrupt (CTIE) will be triggered.

5. Clear CTIF and set the CTIE and GIE register flags to enable the Programmable Counter interrupt.

6. Setup CTB[15:0]. CTA[15:0] will be filled with the same value as CTB[15:0]. When CTA[15:0] overflows, it

will be filled with the same value again. User could decide CTA timeout by setting up CTB[15:0] register.

7. Set TON to start the Pulse Width Measurement.

8. When PFI signal is from high to low, CTA counter will stop counting and clear TON register flag. Interrupt

will be triggered at the same time. Users could read the CTA counter value to know the pulse width of

PFI.

9. If CTA counter overflows, and the PFI signal is still high, the interrupt will be triggered, but CTA will count

again.

CLK

TON

CTA_CLK

CTA 0000

PFII

XXXX

INT

0001 0002 0003 0004 0005

CTIF

0006 0007 0008 0009

Software Write into CTB (CTA same as CTB)

Software Set

When CTIE=1

Figure 6-5 Programmable Counter Pulse Width Measurement mode

FORTUNE'

Properties

For Reference Only